LSU Researchers Go Batty: Graduate Student Studies Bat Behavior

10/27/2011 07:28 AM

BATON ROUGE – Aside from witches and black cats, bats are one of the creatures most synonymous with Halloween – and, perhaps, one of the most villainized mammals in existence. Surrounded by dark superstition, including the allusion of vampirism, the real risk of rabies and a myriad of other diseases, most people don’t give bats another thought beyond the initial reaction of disgust. But researchers at LSU are focusing on the softer side of bats. It turns out that, while most people don’t necessarily give much thought to where bats lay their heads, their roosting rituals and sites can reflect some disturbing trends in the world.

Maria Sagot, doctoral candidate in the department of biological sciences, together with her major advisor, Associate Professor of Biological Sciences Richard Stevens, have made great headway in finding out more about bat society. Bats aren’t always the solitary creatures people often think of, but actually can be quite social creatures operating within family units.

“Tent-roosting bats tend to work in a harem formula,” said Sagot. “Groups tend to be formed by one male and multiple females.”

In other words, she explained, the males control the resource of safe housing, and the females and their offspring live under the care of a single harem-master.

“However, when a male has to fly farther and farther away to get food, he has to leave his harem for longer periods of time, allowing other males to interlope and mate within the harem,” said Sagot. Another possibility is that the females may go to another males’ roost to mate.

Originally, the researchers thought that there might be some correlation between the duration of the refuge and the stability of the social groups of tent-roosting bats, but the opposite turned out to be true.

“What we eventually found is that out of 15 tent-building bat species, all four living in communal tents built from short-lived herbaceous plants form the longest-lasting groups, many maintaining the same company for more than a year,” said Sagot.

In other words, those building roosts with materials that have a short lifespan actually had the strongest community bonds. Read more about this line of research in “Bats Building Bonds” in the May 2011 edition of The Economist, located at http://www.economist.com/node/18648360.

The bats Sagot primarily studies build their roosts in the form of tents made out of palm fronds in the tropics. While their natural habitat is the rainforest, recently more and more roosts have been reported in urban areas.

“They have followed the vegetation as it became integrated into the landscaping models of urban communities,” said Sagot. “We have found that they are increasingly dependent upon the exotic coconut palm, which is only present in human-modified areas.”

This use of urban areas by these bat colonies added a new aspect to their research. Unlike most fieldwork, which typically involves long periods spent in minimal shelter in exotic locations with little to no exposure to other people, this project involved lots of interactions with the local populations in both the Caribbean and Pacific sides of Costa Rica.

“We went from backyard to backyard, asking people if we could check for bat roosts in their coconut palms,” said Sagot. “It was a very interesting experience to watch people as they learned more. At first, people wanted to cut down their palms because they were scared of the bats. But later, as we returned, people grew more excited about the bats in their backyard, pointing out new things they’d noticed. It was an invaluable opportunity to be able to educate locals about these animals.”

Bats are very important to their ecosystems, particularly in the tropics. They’re pollinators, like bees, and seed disseminators as well, and thus ensure the health and vitality of the biological diversity of the rainforest.

“Being able to better understand what drives bats’ habitat selection will allow us a better understanding of the ecology of this area in general,” said Sagot. “Because we were able to explain the importance these bats have to their surroundings, people were able to embrace them instead of fearing them.”

While it might seem like an odd thing to study, both Sagot and Stevens are fascinated by these creatures. And their partnership makes for a great team: she focuses on the behavioral impacts of biology, and he is a biogeographer, giving the team a well-rounded view of the animals they study.

“Bats have more ecological diversity than all other mammals combined,” said Stevens. “They can live in caves palm trees, and anywhere in between.”

Did you know?

• There are more than 1,100 species of bats, with 350 found in the New World (essentially the Western Hemisphere). There are around 12 species found in Louisiana alone.

• They are found on every large land mass except Antarctica.

• There are only three species of vampire bats, and only in the New World. Only one of these actually consumes the blood of mammals.

• A single bat can eat up to 1,000 mosquitoes in a single hour, and can consume more than its body weight each night in insects.

• An anticoagulant derived from vampire bat saliva is now used to treat human heart patients and stroke victims.

• Nearly 40 percent of American bat species are in severe decline or already listed as endangered or threatened. Losses are occurring at alarming rates worldwide.

• Bats one of the world’s longest-living mammals for their size and can live more than 10 years. Some species can live up to 30 years.